Devices for locking the end positions of movable switch parts are known in various configurations. EP 0 603 156 A1 shows and describes an end position securing means for movable switch parts and, in particular, a switch lock in which a pin or rod is guided within a tube, with the rod and the tube being held within an outer tube in an axially displaceable manner. The tube has openings for locking members which are capable of being shifted in the radial direction and, in the known embodiment, are formed by balls or rolls. The rod jacket likewise comprises appropriate recesses at predetermined axial distances so as to enable the locking members, by displacing the rod relative to the tube carrying the locking members, to be displaced either into an external locking position in which they cooperate with stops provided in the outer tube or inwardly so as to render feasible the relative displacement of the tube and the rod in the axial direction. In those known configurations, the tube carrying the locking members was coupled with the switch parts to be adjusted. WO 98/54041, in a modified configuration, proposed a locking device with a hydraulic unit coupled thereto, in which the locking device itself, however, did not form part of the hydraulic actuating means and was guided in a separate, sealed housing. In order to effect also a displacement of the movable switch parts when displacing the rod, the sleeve or rod carrying the locking members must accordingly be entrained by the rod over a predetermined axial displacement path with the displacement forces having to be taken up by the coupling or locking members formed by balls for displacing the sleeve. In order to improve the locking effect, it has already been proposed to mount ring segments on the balls in a manner that the forces in the locking position will no longer be taken up as line-point contacts of the ball, but as forces acting on the annular surfaces of the locking segments. In the locking position, it was thereby safeguarded that the large locking forces in the order of 100,000 Newton could be safely taken up on the respective annular surfaces.
In addition to those configurations, different embodiments of switching aids can be taken from AT 403 683 B and AT 406 038 B, in which an accordingly resiliently designed support of the displacement movement was rendered feasible over a partial region of the displacement path. To this end, either the locking members or the sleeve carrying the locking members were supported via springs in a manner that the sleeve could be displaced over a portion of the displacement path under the support of the spring force as a function of the position of the respective coupling or locking members. The internally arranged rod in such embodiments is connected with appropriate coupling members for the movable switch parts.